This invention relates to internal combustion engines, and more particularly to a method and apparatus for cutting and finishing a cylinder bore surface of such an engine.
Various methods are known for boring, cutting and finishing cylinder bore surfaces of internal combustion engines. In a typical prior art method, a boring tool bores out a cylinder bore. In a subsequent step, a grinding tool machines the bored surface and leaves a pattern of tool marks having a cross-hatched configuration.
The boring tool applies a great deal of concentrated force to the cylinder bore surface, thereby compressing the material near the surface. In a typical prior art method, a thickness of between about 0.0005 to 0.010 inches of material is compressed during the boring process.
Unfortunately, leaving the bore surface material in a compressed state causes problems which arise after the engine is placed into use. One typical problem is that ridges tend to appear on the bore surface which are generally parallel to the bore's longitudinal axis. These ridges are scraped by the piston rings during piston reciprocation, causing metal filings to collect beneath one or more of the compression piston rings. These metal filings tend to scrape against the side of the piston, causing piston galling.